Fine-root traits are devoted to the allocation of foliar phosphorus fractions of desert species under water and phosphorus-poor environments.

Traits of leaves and fine roots are expected to predict the responses and adaptation of plants to their environments. Whether and how fine-root traits (FRTs) are associated with the allocation of foliar phosphorus (P) fractions of desert species in water- and P-poor environments, however, remains unclear. We exposed seedlings of Alhagi sparsifolia Shap. (hereafter Alhagi) treated with two water and four P-supply levels for three years in open-air pot experiments and measured the concentrations of foliar P fractions, foliar traits, and FRTs. The allocation proportion of foliar nucleic acid-P and acid phosphatase (APase) activity of fine roots were significantly higher by 45.94 and 53.3% in drought and no-P treatments relative to well-watered and high-P treatments, whereas foliar metabolic-P and structural-P were significantly lower by 3.70 and 5.26%. Allocation proportions of foliar structural-P and residual-P were positively correlated with fine-root P (FRP) concentration, but nucleic acid-P concentration was negatively correlated with FRP concentration. A tradeoff was found between the allocation proportion to all foliar P fractions relative to the FRP concentration, fine-root APase activity, and amounts of carboxylates, followed by fine-root morphological traits. The requirement for a link between the aboveground and underground tissues of Alhagi was generally higher in the drought than the well-watered treatment. Altering FRTs and the allocation of P to foliar nucleic acid-P were two coupled strategies of Alhagi under conditions of drought and/or low-P. These results advance our understanding of the strategies for allocating foliar P by mediating FRTs in drought and P-poor environments.

Root morphological and physiological traits are committed to the phosphorus acquisition of the desert plants in phosphorus-deficient soils.

BACKGROUND: Phosphorus (P) deficiency in desert ecosystems is widespread. Generally, desert species may allocate an enormous proportion of photosynthetic carbon to their root systems to adjust their P-acquisition strategies. However, root P-acquisition strategies of deep-rooted desert species and the coordination response of root traits at different growth stages to differing soil P availability remains unclear. In this study, a two-year pot experiment was performed with four soil P-supply treatments (0, 0.9, 2.8, and 4.7 mg P kg-1 y-1 for the control, low-, intermediate-, and high-P supply, respectively). Root morphological and physiological traits of one- and two-year-old Alhagi sparsifolia seedlings were measured. RESULTS: For two-year-old seedlings, control or low-P supply significantly increased their leaf Mn concentration, coarse and fine roots' specific root length (SRL), specific root surface area (SRSA), and acid phosphatase activity (APase), but SRL and SRSA of one-year-old seedlings were higher under intermediate-P supply treatment. Root morphological traits were closely correlated with root APase activity and leaf Mn concentration. One-year-old seedlings had higher root APase activity, leaf Mn concentration, and root tissue density (RTD), but lower SRL and SRSA. Two-year-old seedlings had higher root APase activity, leaf Mn concentration, SRL and SRSA, but a lower RTD. Root APase activity was significantly positively correlated with the leaf Mn concentration, regardless of coarse or fine roots. Furthermore, root P concentrations of coarse and fine roots were driven by different root traits, with root biomass and carboxylates secretion particularly crucial root traits for the root P-acquisition of one- and two-year-old seedlings. CONCLUSIONS: Variation of root traits at different growth stages are coordinated with root P concentrations, indicating a trade-off between root traits and P-acquisition strategies. Alhagi sparsifolia developed two P-activation strategies, increasing P-mobilizing phosphatase activity and carboxylates secretion, to acclimate P-impoverished in soil. The adaptive variation of root traits at different growth stages and diversified P-activation strategies are conducive to maintaining the desert ecosystem productivity.

Patterns of carbon, nitrogen, and phosphorus stoichiometry of three life-form desert plants and responses to soil and microbial biomass factors in a hyper-arid desert ecosystem.

Plant, soil, and microbial biomass ratios of carbon (C), nitrogen (N), and phosphorus (P) are crucial in maintaining stability of desert ecosystems. Nevertheless, variation in relations of elemental ratios between different life forms of plants and soil and microbial biomass in desert ecosystems remains unclear. In a hyper-arid desert ecosystem, C, N, and P concentrations and ratios were analyzed in the plant-soil-microbial biomass system of three perennial desert species (Alhagi sparsifolia Shap. [Herb, Fabaceae], Karelinia caspica Pall. [Herb, non-Fabaceae], and Tamarix ramosissima Ledeb. [Shrub]). Concentrations of N and P in Alhagi sparsifolia leaf, stem, and root were significantly greater than those in Karelinia caspica and Tamarix ramosissima, whereas plant C and soil organic C (SOC) were highest with Tamarix ramosissima. Alhagi sparsifolia and Tamarix ramosissima were P-limited, whereas Karelinia caspica was N-limited. According to correlation analysis, SOC rather than soil total P (STP) regulated plant N:P ratios, and microbial biomass C, N, and P rather than SOC, soil total N, and STP regulated plant C:N:P ratios. Soil water content also affected plant nutrient balance. Thus, in a hyper-arid desert ecosystem, the plant-soil-microbial biomass system and the balance of C, N, and P are closely related, and the role of soil microbial biomass in affecting plant nutrient balance should receive increased attention.